1. Field of the Invention
The present invention is directed to a relief system for process fluids under pressure utilizing a pressure fused valve or pressure fused valve actuator to open a relief valve at a predetermined relief pressure. In particular, the present invention is directed to a relief system for process fluids under pressure utilizing a small, pilot pressure activated valve actuator.
2. Prior Art
Many industrial processes incorporate pressurized containers, such as tanks or vessels, and piping to process fluids. Examples of such industrial processes include natural gas processing, oil refining, and chemical manufacturing. Examples of component equipment include pressure vessels, drums, tanks, pumps, compressors, blowers, and distillation columns. These industrial processes are required to operate within acceptable pressure ranges. Changes in temperature, equipment status, and power conditions, among others, may cause the pressure in the containers or in the process to rise. By way of example, a closed process outlet or a plant fire might result in an over pressure condition.
While it is possible to design tanks and other parts of the industrial process to withstand extremely high pressures, it is also important to have pressure relief systems in place that may be opened to divert the fluids in the event of pressure over the predetermined level. In addition, government regulations and industry codes may require protection against over pressure. For example, see U.S. Code of Federal Regulations, 29 CFR §1910.119 on Process Safety Management.
While it is possible to monitor an industrial process and manually open relief valves in the event of an over-pressure condition, it is also important to have a system in place so that valves will automatically open, thereby diverting fluid and reducing the pressure.
In some industrial processes, such as natural gas processing or oil refining, in the event that a relief condition is determined, a valve or valves will be opened and the excess hydrocarbons will be directed to flares so that the process fluids will not be released directly to the atmosphere.
Various types of relief valves are used to control or limit the pressure in a system or vessel. The relief valve may be designed or set to open at a predetermined pressure in order to protect the vessels and other equipment. When the predetermined pressure is exceeded, the relief valve will be forced open and fluid will be diverted through an auxiliary route. As the fluid is diverted, the pressure inside the vessel or tank will drop. Once it reaches the resetting pressure, the valve will be reset or re-closed.
In order to quickly and safely reduce the pressure in the system, high flow capacity may be required to quickly reduce pressure upon opening of the relief valve. One type of relief valve incorporates a buckling pin. In the event that a buckling pin relief valve is used as the relief valve, the throughput capacity is limited by the physical dimensions of the moving end of the buckling pin valve upon buckling pin failure.
Accordingly, it would be desirable to provide a relief valve system that could utilize a small fused actuator while permitting adequate fluid flow in the event of an emergency or in the event of controlled relief.
Moreover, existing buckling pin valve designs are difficult to test while the system is under pressure on line. Testing of the existing buckling pin valve designs requires either taking a portion of the system off service which reduces the system capacity or the addition of rather large and expensive isolation valves. Accordingly, it would be desirable to provide a buckling actuator valve design that would be simple to test without taking a portion of the system off service.
It would also be desirable to provide a relief valve system that could be operated automatically in the event that the system exceeded a predetermined pressure or alternatively might be manually or electronically opened with an actuator.
It would also be desirable to provide a relief valve system that utilizes readily available components without expensive custom components.